Abstract
Abstract: :
Purpose: The objective of the current study was to examine the role of media volume, feed, gas exchange and incubation time on encapsulated cell performance in vitro and in vivo. Methods: Two genetically modified mammalian cell lines (NTC-201-10 and NTC-201-6A) secreting low and high levels of CNTF were encapsulated within a polymer membrane and placed in holding packages containing either 2, 20 or 40 mL of culture media. The media in the 2 mL volume package was replaced weekly and exposed to 95% humidity and 5% CO 2 . Packages containing 20 and 40 mL of media were closed to the environment with no air headspace and no media replenishmet following closure. All packages were maintained at 37°C for 2-weeks, 1, 2, 3 and 4 months post-encapsulation. At each time point, some of the encapsulated capsules from each treatment group were evaluated for CNTF output and cell viability, and some were surgically implanted into the vitreous of individual eyes of rabbits. After 1 month, the devices were explanted and evaluated for CNTF production and cell viability. Results: Capsules in the 20 and 40 mL closed packages produced higher level of CNTF compared to 2 mL open packages. For the encapsulated NTC-201-10 cell line, CNTF production decreased in the 2 mL and 20 mL packages while remaining steady in the 40 mL group over time. For the encapsulated NTC-201-6A cell line, CNTF production remained steady in the 2 mL package and increased in the 20 mL and 40 mL packages, initially, and reached steady state at two months. In all cases, the CNTF production of explanted capsules were statistically equivalent following a 1-month implantation period. Histological evaluation confirmed that all capsules contained viable cells. Conclusion: Encapsulated CNTF secreting cells can be maintained in a closed environment without media feed and gas exchange. Media volume of 40 mL seems to be ideal for both cell lines. Although some variations in CNTF output were observed after encapsulation in capsules held in vitro, their in vivo performances are consistent.
Keywords: 423 growth factors/growth factor receptors • 629 vitreous • 567 retinal pigment epithelium